1. Field of the Invention
Aspects of the present invention relate to an injection mold apparatus, and more particularly, to a weldless-type injection mold apparatus, which can reduce a heating time and a cooling time of an injection mold when heating and cooling the injection mold by forming a heat blocking unit.
2. Description of the Related Art
An injection molding process is to plasticize a polymer resin by applying heat thereto to then inject a molten polymer resin into a mold using a hydraulic pressure and enables mass production of standard products of various sizes.
A general forming process of a polymer resin has problems, such as an aesthetically poor appearance due to a weld line formed by the molten resin in the mold and a low degree of surface gloss.
To solve these problems, a heating molding method is widely used, in which a mold temperature is set to be higher than a melting point of a formed polymer resin. Examples of the heating molding method may include Japanese Patent Publication No. showa 45-22020 (Heating method using hot wind), Japanese Patent Publication No. showa 51-22759 (Heating using electric heater and water cooling), Japanese Patent Publication No. showa 55-109639 (High-frequency inductively heating), Japanese Patent Publication No. showa 57-165229 (Heating by applying vapor into cavity), Japanese Patent Publication No. showa 61-79614 (inserting a heated plate between cavity and core), and Japanese Patent Publication No. hei 4-265720 (Mold surface heating using electrically conductive layer).
However, if the polymer resin is formed by setting a temperature of a mold to be higher than a melting point of polymer resin, a weld line is not formed while enhancing aesthetic appearance, such as gloss. However, a high temperature of the mold extends a cooling time, and the overall forming cycle may be prolonged, thereby lowering the manufacturing efficiency. In particular, since the polymer resin is not separated from the mold after being cooled to lower than the melting point thereof, deformation due to shrinkage may become severer than in the general molding.
As described above, these prior art mold heating methods, which were initially used, are problematic due to a low heating rate for heating the mold surface, so that a heating time is extended and the overall cycle time is prolonged, thereby lowering the manufacturing efficiency. In addition, if the temperature of the mold is elevated to a considerably high temperature, a cooling time may be extended.
In consideration of the foregoing, there have been proposed a mold temperature automatic control system, as disclosed in Korean Patent No. 00811909, a mold cooling system, as disclosed in Korean Patent No. 0167711, a mold temperature control system, as disclosed in Korean Patent No. 0470835, and a system of rapidly heating and cooling a mold in a range of 100° C. to 200° C./min, as disclosed in Korean Patent No. 0701229.
In the disclosed systems, however, cooling and heating of the mold are performed within a very short time. Thus, the foregoing problems are not overcome. In particular, since many cooling lines and hot water supply lines are provided for cooling and heating the mold, the mold has a relatively weak structure and is liable to deform by repeated formation processes. In the conventional mold, a lead is formed at a lower portion of the mold located to correspond to the cavity, thereby reducing heat capacity for heating and cooling. However, if the lead is formed at the lower portion of the mold, the mold may become relatively weak, resulting in creation of cracks due to external impacts or repeated injection molding processes.
Meanwhile, in the conventional weldless-type mold apparatus, the mold may be entirely heated such that heat is diffused to a region other than a cavity region (to an opposite side of the cavity) during heating using a heat source. In addition, as an injection molding time of a product is extended, heat may accumulate in a mold for injection molding.
To address these problems, the inventor of the present invention developed a weldless mold, and filed applications for the developed weldless mold (Korean Patent Application Nos. 2007-045726 and 2009-0104541). After continuous research and development, the inventor has completed the invention.